KEYCTL_DH_COMPUTE(3) Linux Key Management Calls KEYCTL_DH_COMPUTE(3)
keyctl_dh_compute - Compute a Diffie-Hellman shared secret or public
long keyctl_dh_compute(key_serial_t private, key_serial_t prime,
key_serial_t base, char *buffer, size_t buflen);
long keyctl_dh_compute_alloc(key_serial_t private,
key_serial_t prime, key_serial_t base, void **_buffer);
keyctl_dh_compute() computes a Diffie-Hellman public key or shared
secret. That computation is:
base ^ private ( mod prime )
When base is a key containing the shared generator value, the remote
public key is computed. When base is a key containing the remote pub‐
lic key, the shared secret is computed.
base, private, and prime must all refer to user-type keys containing
the parameters for the computation. Each of these keys must grant the
caller read permission in order for them to be used.
buffer and buflen specify the buffer into which the computed result
will be placed. buflen may be zero, in which case the buffer is not
used and the minimum buffer length is fetched.
keyctl_dh_compute_alloc() is similar to keyctl_dh_compute() except that
it allocates a buffer big enough to hold the payload data and places
the data in it. If successful, a pointer to the buffer is placed in
*_buffer. The caller must free the buffer.
On success keyctl_dh_compute() returns the amount of data placed into
the buffer when buflen is non-zero. When buflen is zero, the minimum
buffer length to hold the data is returned.
On success keyctl_dh_compute_alloc() returns the amount of data in the
On error, both functions set errno to an appropriate code and return
the value -1.
ENOKEY One of the keys specified is invalid or not readable.
EINVAL The buffer pointer is invalid or buflen is too small.
One of the keys was not a valid user key.
This is a library function that can be found in libkeyutils. When
linking, -lkeyutils should be specified to the linker.
Linux 07 Apr 2016 KEYCTL_DH_COMPUTE(3)